The present invention relates generally to agricultural implements, and more specifically, to implements for incorporating chemicals or small grains into the soil.
Chemicals have become widely used in the farming industry. Typically, a chemical is applied to the surface of previously worked soil and a maximum of two additional tillage passes are made either with a disk or field cultivator to incorporate the chemical into the upper few inches of the soil. Although some farmers eliminate the recommended second incorporation pass, they must rely on favorable weather conditions to prevent failure, and horizontal and vertical distribution patterns of the chemical often are much less than optimum. Although surface applied chemicals are available at a higher cost, they are usually incorporated by rainfall and there is a considerable amount of risk involved with such a chemical since rainfall is highly unpredictable. Often the cost of chemicals which eliminate incorporation passes exceeds the combined cost of the tillage and chemicals they replace.
Where two incorporation passes with a conventional tool are not necessary, special harrows or S-tine cultivators have been devised for use in one or more passes. These tools are limited to shallow incorporation of herbicides in low residue environments. Another popular approach has been to combine the tillage of two passes into one pass by combining the components of two conventional machines into one frame. However, the price and the draft are approximately doubled The advantage of making passes in different directions has been lost, and therefore streaking and marginal performance are common with many of the available incorporating devices. Combining tillage work also reduces the versatility of an implement. For example, if a late mechanical weed kill is desired, all tillage must be done just prior to planting. This can require a very large tractor in order to stay ahead of a large modern planter. Although disks and field cultivators can provide adequate incorporation in some circumstances, they generally require a high energy consumption and a massive frame. Streaking or banding of the chemicals is common, particularly when a disk with large and widely spaced disk blades is used. The operating speeds, and thus the productivity, of these types of machines are often limited to beyond the level which is satisfactory to the farmer.
Although some rotary incorporating machines have been available on the market, these have not been entirely satisfactory for one or more reasons. Some rotary hoe type of weeders having a single transversely extending row of spider wheels have been utilized to incorporate pre-plant chemicals. However, these can only be used in certain conditions and where incorporation is not critical, or alternatively, where two passes of the rotary hoe are utilized. A single row of rotary hoe spider wheels tends to cause the chemical to streak, leaving hot bands of chemical where crops can be damaged or destroyed while leaving other areas substantially void of chemicals. Often the spider wheels designed for rotary hoeing to remove small weeds and break up surface crusts are not suitable for mixing soil. The tines of such hoes are typically triangularly shaped with a principle design criteria being easy entry into the soil. Unless there is adequate depth control of the spider wheels, the wheels can act more like solid disks, pushing the soil to one side rather than letting the soil flow through the tines and mix and incorporate the chemical. Other types of rotary incorporators use two or more angled gangs of spider wheels spaced fore-and-aft with respect to each other. Typically the forward gang is angled with respect to the transverse in an opposite direction as compared to the rearward gang. Numerous pairs of the fore-and-aft spaced gangs are located transversely along a large frame with adjacent gangs being angled in opposite directions with respect to the transverse to generally equalize side forces along the width of the machine. In an implement where such gangs are used, the area between adjacent gangs produces a discontinuity in the soil throwing and mixing action as compared with the action within the confines of the gang itself. Also, the outermost wheels of the machine tend to throw dirt and chemical beyond the width of the machine so that there is ridging and chemical mixing variations adjacent the edge of the machine. Although such machines may have improved incorporation as compared with a conventional disk arrangement, a massive and expensive frame is necessary to support the gangs of spider wheels. Therefore, such an implement is comparable in size and in price to a disk or other conventional tillage implement.
Previously available rotary type incorporators often include tandem sets of spider wheels closely spaced fore-and-aft so that in trashy conditions the wheels may plug. Some arrangements utilize a wheel support arm closely spaced to the spider wheel, which also presents a potential clogging problem in trashy conditions. The spider wheels themselves often are of the type wherein the opening between the teeth decreases substantially in the direction toward the hub to thereby cause wedging of trash. The tooth profile is often designed to provide easy entry into the soil rather than providing good cleaning characteristics which are necessary in heavy trash.